Trouble Comes in Threes
by Hi Pot And News
Summary: AU. Fem!Harry. John and Sherlock investigate a bizarre case. Meanwhile, A certain Muggle Studies class is on field-trip.


**AN:** A little pre-Christmas present for my readers who enjoy this category! It might remain a one-shot, but if I add more, it won't get any bigger than three chapters.

First Sherlock fic and crossover! Please be gentle; I didn't pay much attention to the little details when watching the show and I'm only familiar with crossovers featuring it. Also know that I'm a Thai-American that's only ever travelled through the southern U.S. and South-east Asia; I have absolutely no knowledge of the geography of England, so I'll likely be messing up quite a lot of it.

* * *

 **NOTE** : This story begins after season 1, but before season 2 begins. Since there are time skips between episodes and longer time skips between seasons, I am writing under the assumption that John and Sherlock have completed many cases that we just never hear about during the show.

* * *

 **O** ne of the dubious benefits of living with Sherlock and spending most of one's time with him was meeting all sorts of people, usually odd ones at that. Not including the criminals they caught, John had made the acquaintance of several peculiar characters, from morgue-workers to circus performers. Not to say that there was anything _wrong_ with being peculiar, but they were certainly not the sort of people John would meet without Sherlock's influence.

On that day, the two of them were looking into what looked to be (incredibly) Spontaneous Human Combustion. And not just one, but _two_. The scene of the . . . crime? Accident? Act of God? The location of death was a well-kept barbershop within Trafalgar Square. John had never seen anything like it, and only the lack of any possible ignition source nearby made him come to such a conclusion.

The owner of the barbershop, a greying chap by the name of Roderick Bode, was a terrified mess. According to him, he had been cutting the hair of a last-call customer, and had went into the back to get some more conditioner. While in the back, he then heard the chime of the shop door open, and had called out that he would be right there. Then there was shouting, so he ran to the front. When he got there, his customer and the person that had just come in were both covered in flames.

He had tried to put them out, Mr. Bode continued, but they were already on the ground and burnt black when he got there. He had then run out of the shop and called 999 immediately.

John couldn't do anything but believe the distraught man; there was no sign of foul-play from what he could see. Sherlock himself seemed to be of the same opinion, though his puckered brow gave away his displeasure at such a preternatural conclusion.

"I suppose next we'll have someone claiming alien abduction," Sherlock grouched as they surveyed the team of paramedics collecting the scorched remains.

The front of the shop had been roped off. There was a loose ring of the morbidly curious hanging about the policed area, but the on-lookers didn't linger for the most part. The Square was heavily trafficked that day with shoppers and tourists, what with it being late afternoon on a weekend, and such a scene was likely more excitement than they had been expecting.

"Come now," John cajoled, "Such cases are rare, but they're not exactly outside the realm of possibility, are they? There's been many documented accounts of Spontaneous Combustion, so it can't be considered pseudo-science, can it?"

Sherlock scoffed. "By that logic, Elvis still lives amongst us and there is indeed a Loch Ness Monster."

"I wouldn't call Nessie a monster," said a blithe voice from behind them.

John started and turned to see a pale-blonde young woman a few feet left of where he and Sherlock were standing. She was dressed in an open black blazer, a blouse, and a blue waist-coat over a calf-length full skirt, and was wielding a black umbrella much like one would a cane. She had a dazed look about her, as if she had been smoking something particularly strong, and she was staring into the window of the barbershop with a vaguely sad look on her face.

"Excuse me?" said John, wondering how she had gotten so close without him noticing.

"Despite the folklore behind them," the girl continued, reaching a hand up to twirl a lock of her long hair, "kelpies generally aren't belligerent when unprovoked, and usually only so when their personal territory is invaded. Rather like kangaroos."

It took John several blinks before he could restart his brain and come up with a response to such a brazenly whimsical statement from so far out of left field. In contrast, Sherlock suffered no such inhibition.

"Kelpies, you say," said Sherlock, a measuring look on his face. "You believe them to be real?"

John couldn't tell if Sherlock was asking in earnest or if he was mocking her.

"The nice thing about creatures like kelpies," the girl replied dreamily, still not looking at them, "is that they don't need me to believe in them to be real. Imagine if the existence of things depended on how much people's belief in them there was: the earth would be flat and carried on the back of a giant turtle that swims through space, and snorting powdered ginger would cure epilepsy. It's comforting to know that kelpies, like mooncalves, are things that won't just stop existing."

Even Sherlock didn't have anything to say to that. John imagined that the uncomprehending look on Sherlock's face was doubled on John's own.

That was when he heard the click of a camera going off. Compounding onto the bizarre situation they had found themselves in, another young woman entered the scene, this one with dark auburn hair, viewing them from behind an old fashion Polaroid camera. She was dressed similarly to the blonde girl — umbrella included, hanging from the crook of her elbow — except with a red waistcoat instead of blue. This made John think that they were in school uniforms, what with their apparent age.

He had never seen a uniform so business-formal before though. They must have come from some posh public school*.

"I didn't expect such a photo opp today," she said absently, clicking another picture and shaking the photo lightly when it came out. She hummed with satisfaction as she looked over the results.

"Harrington," said Sherlock, his tone blander than usual.

John glanced up to see his friend's flat, irritated expression.

The red-head's lips tilted into a knowing smirk. She lowered her camera to reveal arresting green eyes, and matched Sherlock's flat expression with an unimpressed one of her own, lids half-mast and eyebrows raised inquisitively.

"Sherlock," she replied, her tone almost mocking.

"Shouldn't you be in school?" said Sherlock, taking a few threatening steps closer. "Don't tell me you've run off again."

The girl scoffed lightly, raising her camera again and clicking a picture of Sherlock's disapproving face before he could wave her off. She easily side-stepped toward the still dazed blonde when Sherlock swatted at her. She waved the photo teasingly at him.

"Guess again," she said, her expression still mild and unintimidated.

Sherlock's eyes narrowed at her, giving her a quick once-over.

"A field-trip?" he suggested, his expression lightening into his contemplative look. "I wasn't aware you took part in this class. Why was I not informed?"

The girl waved a hand dismissively before returning her attention back to her camera.

"I figured you wouldn't care," she replied, moving closer to the barbershop and taking a few shots of the interior. As she flitted about, she absently handed the photos to the blonde girl — with a murmured, "Hold these, would you, dear?" — confirming to John that they knew each other at the very least. "It was just made a core class this year anyway."

Her words were punctuated with the clicks of her camera as she took multiple shots of the scorched store-front and bodies. Though the paramedics and on-duty officers looked to be in varying states of put-out and displeased at the casual irreverence, she wasn't actually obstructing them in any way, so they made no motion to stop her.

"I see," said Sherlock, amusement drawing up the side of his mouth ever so slightly. Apparently, there was more to the girl's innocuous statement, though what hidden meaning was behind such an everyday assertion, John didn't know. "So, the administration hopes to remedy the rampant bigotry borne from ignorance that has been causing so much conflict amongst you."

What? What did a class field-trip have to do with battling discrimination?

"That's a bare-faced way of putting it," the girl replied, peering at an excellent shot of a hand that was more blackened bone than flesh.

"How do you find their efforts so far?"

She snorted scornfully, giving the burnt-hand photo over to her friend as well. She returned to standing in front of Sherlock and put her hands on her hips.

"The professor's so wrapped up in being politically-correct and progressive that he ends up offending the students he panders to. You should hear him when he starts raving: ' _The ingenuity of commoners!'_ " she gushed exaggeratedly, affecting a chirpy Irish accent. " _'They haven't the time or the means to eat proper food, so they invent alternative sustenance! What say we sample from this McDonald's? I've been told it tastes like actual food!'_ Hermione's quite put out with him."

"' _Commoners'_?" Sherlock echoed, derision re-entering his tone. "Is that what's it's called now?"

She flicked her hand dismissively. "It's bit uppity, but there's a distinct lack of words we can use without drawing attention to . . . well, the _differences_ between us. 'Mundane' was suggested, but Hermione argued that _that_ was equally as offensive and possibly leading as well."

" _Excuse me_ ," John cut in shortly, finally at the end of his rope. "But _what on earth_ are you talking about?"

The red-haired girl looked at John in surprise, blinking rapidly.

"I beg your pardon?" she said, cocking her head to the side.

"It's just —" John began, struggling to vocalize his bewilderment. "First it was— and then you— and-and . . ." he blew out a breath and ran a hand through his hair in frustration. Deciding to address the main part of his confusion, he said, "How do you know Sherlock?"

Another flutter of lashes.

"You know Sherlock?" she asked. She would have looked gobsmacked if it wasn't for the blankness.

John frowned in confusion.

"Well, yes, of course," he said. "Why else would I be standing here with him?"

Her cheeks gained a tint of pink.

"I beg your pardon," she said again, this time with contrition. "Sherlock has always gone on about not needing friends — 'unnecessary distractions' he's said — so I assumed that you had just happened to be standing rather close. It was not my intention to ignore you, sir."

"Assuming things again," Sherlock jeered, turning his nose up. "I've told you that it's a habit that would do you no favours."

The girl re-donned her unimpressed look.

"Spare me."

John gave Sherlock a significant look, one Sherlock returned blankly. John held back a huff. Honestly! The lack of social-awareness of the man!

"Introduce us to your friend, Sherlock," the girl said, giving John a sympathetic, commiserating look. "It's only polite after having a conversation without including him."

There was a look of what could be argued as a sulky pout on Sherlock's face.

"Dull," he grumbled, re-adjusting his scarf. He sighed gustily when her hand darted out and prodded him in the side. "Fine, fine. This is my flatmate and business associate, Dr. John Watson. John, this is my cousin" —WHAT? _Another_ Holmes?! — "Harrington. I haven't been introduced to her little friend."

The red-haired girl smiled softly and spread her skirts in a curtsey*.

"Delighted to meet you, Dr. Watson. Please, call me Harry."

"Ah, yes!" John gave a jerky half-bow awkwardly. "A pleasure. And — and John's fine."

"This is my friend, Luna Lovegood," Sherlock's cousin — Harry — said. She ushered the unfocused blonde to stand beside her. "We're here with our . . ." she glanced at Sherlock, "Contemporary Civilization Studies class for hands-on observation of the everyday people."

"A pleasure," said the blonde, blinking hazily at John. "I've never met one of the mundane folk before; your aura is a lot brighter than I was expecting."

John had been feeling vaguely offended since this conversation began; at this point, he didn't know if he was flattered at the queer girl's comment or more offended than ever. What was he supposed to say to such an unusual and back-handed compliment?

"R-right . . ." said John, looking at Sherlock in askance. "Why didn't you tell me that you had a cousin?"

"What occasion has there been that it would have been significant to inform you that I have extended family?" asked Sherlock, looking bored. "Harrington has nothing to do with our day-to-day living, nor has her existence impacted the operational performance of our cases in any way. Such information was inconsequential."

"Sherlock!" John scolded. "What a callous thing to say!"

John had known that Sherlock didn't care much for his brother, but he hadn't realised that the sentiment extended to the rest of his family as well. John wondered what the genius' mother was like, having such an unattached son.

Harry — _that_ would get confusing fast — only smiled blandly in response, seeming to be completely unbothered.

"Not to worry, sir," she said, brushing down the front of her skirt demurely. "It's the same reason why I haven't told my friends about Sherlock before either. The majority of my friends aren't even aware that I have more than one cousin."

John suppressed a wince. What was with this family that they were so immodest about having so little regard for each other?

"It's not that we don't care for each other," Harry remarked, making John start. "It's just that we're not the type to offer up information frivolously. It would have fulfilled no purpose for Sherlock to speak of me before, therefore he didn't. And despite what they might have said about each other, Sherlock and Mycroft have yet to fully suppress their brotherly love, no matter how hard they've tried."

"How did you . . . ?" John began, looking at the young woman with confusion. He glanced up at Sherlock to see the other man looking sour. "Can you do that observation thing they do as well? Is it some trait that runs in the family, then?"

"Of a sort," she said amicably. "Though I'm afraid my talents are a bit different than what Sherlock and Mycroft boast."

"Oh?" said John, interested despite himself. It was hard imagining Sherlock as anything but a one-in-a-million personality; a whole family of Sherlocks was mind-boggling.

"I would hardly call such a pale facsimile of my practise anywhere near equal standing," said Sherlock sharply, looking properly insulted. "My deductions are based on _science!_ Logic and critical thinking! Her suppositions are nothing more than—!"

He cut himself off abruptly and glowered at the ground.

"Nothing more than . . . ?" prompted John, watching his friend expectantly.

A smirk grew on Harry's face as Sherlock scowled.

" _Intuition_ ," they said in chorus, the girl tutting when Sherlock all but spat the word out, as if it was some filthy invective.

"I didn't know that your cousin suffers from the Hairy Heart," said the Lovegood girl, looking to Harry with concern. "I would have made some otter oil ointment for his glabella."

John did not restrain himself from outright goggling at the bizarre young woman any longer. _'Otter oil ointment . . .'_

This was all Sherlock's fault, John just knew it.

"Never mind Sherlock's affliction, poppet," Harry told the other girl consolingly. "He's lived with it long enough that he's proved himself superior even with the handicap. Though he would argue that it's a blessing rather than a curse, of course."

"In any case," Sherlock said crossly, "any affliction I might come across will be cured by _verified_ modern medicine, not a questionable brew concocted by some quack of a witch-doctor."

The Lovegood girl did not get offended like John was expecting. If anything, she became more concerned.

"It's worse than I thought," she said, blinking watery blue eyes up at Sherlock. "He's suffering from a mundane mind. We should introduce him to Hermione so she could tell him about her own recovery. I've heard talking about it encourages the impaired to seek proper avenues of rehabilitation."

This was a method of combating Sherlock's abrasiveness John had not considered before: being just as nonchalantly offensive as he was, with a side of cloud-cuckoo-lander. John could see that his friend wasn't well equipped to deal with this strange new retaliation, especially since his opponent didn't seem to have even realised they were competing.

Sherlock's cousin seemed to be amused it though. John supposed she would _have_ to derive some amusement out of the other girl's peculiarity to be friends with her.

"I think," Harry said, "that Hermione would be more likely to 'relapse' if such a meeting would occur. Between the two of them, I think Sherlock would be the dominant personality, and we wouldn't want them to encourage each other on that front, would we?"

"The babies they'd make would be depressingly unimaginative," Luna said in what was assumed to be agreement. "Commonsensical even."

Before John could start thinking of ways to politely extract Sherlock and himself from the bizarre situation, a gaggle of students dressed much like the two girls before them came around the lion statues and towards the fountain nearest to where the four of them currently stood. John wouldn't have normally noticed them on such a heavily-trafficked day like today was turning out to be, but it was hard _not_ to notice them when they were travelling in almost a huddle and the teacher leading them was looking a bit frantic. If that wasn't enough, there was an air around all of them that was distinctly . . . _separate_ — much like the two young women in front of him and even Sherlock had.

Merciful God, John was beginning to get the impression that there was some sort of vocational school _made_ to produce Sherlocks. If John was developing a nervous twitch at the thought, it was nobody's business but his own.

"What of the umbrellas?"

John snapped out of the beginnings of his nervous break down to see Sherlock frowning at the crowd of students. Sure enough, each of them was carrying an umbrella. What an odd uniform requirement. John absently noted that the umbrellas matched the colours of the waistcoats of the students carrying them, either red, blue, yellow, or green.

It was Luna that answered.

She said, "Professor O'Heachthighearna decided umbrellas would be good camouflage. I'm not sure why he thought that though — it's not like umbrellas grow naturally around here."

Sherlock gave the blonde a look with askance before giving his cousin a pointed stare.

"It's not like you can't already guess," Harry replied, lifting a shoulder. "It was decided that we needed a way of blending in with commoners without completely inconveniencing ourselves." — why they needed to 'blend in' at all or even what that had to do with umbrellas John didn't know — " _I_ suggested tattoos so we wouldn't have to keep track of what we're carrying, but the professor said it was too drastic a measure.

"Of course," here she held up her hand, revealing vaguely Asiatic script circling her palm, "I went through with it myself, but that was more because I wanted to see what it would be like rather than I thought it necessary."

Sherlock gave the odd tattoo as morbidly amused once-over as John stared at the terribly out of place body-art. John was so lost at this point that he wondered if there was any point in continue to follow the conversation.

"Mycroft will be furious," Sherlock said almost gleefully. "You know how he gets when you do something he deems 'unladylike'."

Harry actually rolled her eyes.

"If I wanted to brand a Satanic ritual circle to my belly and take up smoking from a corn-pipe, it would still be none of his business. Mycroft should have better things to do than badger me about a perfectly useful tattoo."

"Harry! Luna! There you two are!"

A curly-haired young woman wearing a uniform with the same colouring as Harry waved her arm to get their attention. She had separated herself from the crowd of other students that were already being herded away by the still agitated teacher. She had a ruffled air around her, as if she had been dealing with some shit for longer than she had been willing to, but considering she was acquainted with the two young women that were currently throwing John through loop, it wasn't very surprising.

Trotting up, she gestured impatiently.

"Professor O'Heachtighearna has been out of his mind with worry since you two ran off! What were you thinking? We're already gathered up to leave and we couldn't find you!"

"Calm down for goodness' sake. Don't you want to be introduced to these fine gentlemen here?" Harry said in response, looking not at all bothered by the scolding.

The curly-haired girl put her fists to her hips and puffed up with indignation.

"You can flirt with older men _later_ , Harrington!" She looked to the sputtering John and blank-faced Sherlock. "I'm sorry to cut this short, but we're on a very tight schedule. We can't be late or we'll miss our flight back to school."

With that, she latched onto Luna's arm and pulled her forward, tugging her along as if she expected the blonde to wander off again if not made to follow.

"I suppose I'll be going now then," said Harry, waving a hand in farewell.

"Wait," commanded Sherlock, grabbing onto her shoulder. "What of the photos?"

For a moment, John had no idea what Sherlock was talking about, but then he saw Harry tuck a handful of Polaroids into her blazer pocket. Right, she had been taking pictures of the remains of the fire.

"No need to concern yourself about it," she said. "Suffice to say, this matter is a bit beyond your usual."

Sherlock frowned heavily.

"You mean . . . ?"

"Yes," Harry replied, confirming whatever it was that Sherlock was asking. "I would normally leave you to it either way, but this would just be a waste of your time. It's actually pretty open and close. The photos are just for the record."

"Harry!" the curly-haired girl called when she noticed Harry wasn't following.

"Better go before she blows her top off," said Harry, pulling out from under Sherlock's grip. "It was nice talking to you."

Sherlock watched the girl go with an irritated scowl on his face.

"So . . ." John trailed off. He scratched the back of his head. Suppose it was time to get back on track. "Shall we go tell Lestrade that it was a case of Spontaneous Combustion now?"

Sherlock huffed and stuffed his hands into his coat pockets.

"Never mind the case, John," he grumbled. "There's no use in thinking on it any further."

With that, he turned and began walking in the general direction of their flat.

It took a moment for John to understand what just happened. When it finally clicked, he hurried to catch up to his capricious companion.

"What do you mean 'never mind'?" John demanded. "Since when do you just abandon a case?"

"Assuming your hearing has not begun failing you at random intervals, you must have heard Harrington say that continuing to pursue this matter would be a waste of our time."

"And . . . and you just accept that?"

Nothing had been making sense since they had arrived at the barbershop, and John was feeling quite a bit sore at Sherlock for prolonging the insanity.

"There are matters beyond your knowledge at work, John. Suffice to say, when it comes to matters that my cousin specialises in, I am more than willing to leave those matters to her."

* * *

 **AN: Regarding the first *! Confused Americans take heed!:**

To Americans, 'public school' means that the school is government-funded and that anyone can attend, meaning that it's open to the general public; 'private school' means the school is privately owned, and there are certain standards a student must meet as well as a fee that must be paid to allow entry. It's stereotypically believed that only snobby rich-kids attend private schools. To the English, it's the other way around. So when John says Harry and Luna must attend a public school, he means that they go to some super-fancy private school.

 **Second *:** Does anyone else do this? The school district I was a part of as a child taught us how to bow and curtsey and how to do abbreviated forms of it depending on how polite you needed to be. I had always assumed it was just a thing you did when you wanted to extra polite, but I've been told that it actually wasn't taught in other school districts and that it's more formality than required in everyday interactions.


End file.
